1. Field of Invention
The present invention relates to a light module for a motor vehicle headlamp.
2. Description of Related Art
Light modules are known in the art. For example, published German Patent DE 10 2008 036 192 discloses at least one first light source, a primary lens, an aperture shutter and a secondary lens. The primary lens is configured to convey light emitted from the light source to an intermediate light distribution lying between the primary lens and the secondary lens. The aperture shutter has a coherent outer edge and an aperture shutter surface, which extends into the intermediate light distribution, and which is bordered by an aperture shutter edge. The aperture shutter is disposed in relation to the secondary lens such that the aperture shutter edge is projected by the secondary lens as a light/dark border in a second light distribution, which is generated as an image of the intermediate light distribution by the secondary lens in a foreground of the light module. The primary lens is disposed in relation to the secondary lens such that the secondary lens distributes light in the intermediate light distribution, which passes by the aperture shutter on one first side of the aperture shutter in a first beam path, in a region lying on one first side of the light/dark border in the second light distribution.
A module of this type generates a light distribution having light/dark borders, such as, for example, a low beam or fog lights. Depending on the design, a light module of this type having at least one further light source and one further primary lens as well, is also suited for generating a high beam light distribution using the same secondary lens.
Light modules of this type are also known as projection systems. They include one or more LEDs as the light source, having associated focusing lenses as the primary lens, a horizontal aperture shutter, and a projection lens as the secondary lens. A light module is known from DE 10 2011 004 569 A1, which uses a reflector as the secondary lens. The invention can also be used with light modules of this type. A light/dark border is generated by the aperture shutter, so as to avoid blinding oncoming vehicles.
One disadvantage of projection systems known in the art is that only a small amount of light ends up in the region above the light/dark border, such that objects (for example, traffic signs) are not sufficiently lit. In order to not blind oncoming vehicles and to ensure a sufficient recognition of objects in this dark region, there are government-mandated regulations that require light intensities between 64 and 625 cd in a region of typically 2 to 4 degrees in the vertical direction and −8 to 8 degrees in the horizontal direction. This region is frequently referred to as the “overhead” region. The degree specifications for the vertical direction relate thereby to upward deviations from a longitudinal direction of the motor vehicle. The degree specifications for the horizontal direction relate to deviations to the right and left from the longitudinal direction. The vertex of the angle is located in the light module thereby. In order to obtain these light intensities in the overhead region, the use of a lens which exhibits structures that deflect light into the overhead region as the secondary lens, is known from EP 1 980 787. A similar solution is described in EP 464 890. However, in each case, the structures are disadvantageously outwardly visible to an observer of the headlamp, which has a negative effect on the appearance of the headlamp. In particular, at night, the regions of the lens that diffuse the light are visible to the observer as bright points, lines, or areas, and are thus disadvantageous in terms of the appearance of the headlamp.
With the subject matter known from DE 10 2009 020 593, light is deflected to the overhead region with numerous small prism structures on a lens. This solution also has the disadvantage that the small prism structures are visible to the observer of the module. The micro-prisms deflect light in a preferred spatial direction, but the micro-prisms act as diffusion structures at their edges, which, in actual components, have a rounding that scatters light in a large spatial angular region. As a result, the small prisms appear as bright, in contrast to the rest of the surface of the lens, when viewing the lens from a region lying above the light/dark border of the light distribution generated by the module. This is typically the case when viewing an automobile from the front, the headlamps of which use projection lenses provided with prism structures of this type as secondary lenses. This appearance is frequently undesired.
In U.S. Pat. No. 6,736,533 and in EP 624 753, in each case, a solution is described wherein light is deflected above the light/dark border with an additional reflecting aperture plate lying between the aperture shutter edge of a first aperture shutter and the secondary lens in the beam path. The disadvantage with this solution is that it cannot be used with a light module that is a combination of a low beam light module and a high beam light module and having a horizontal aperture shutter (see EP 1 980 787). This is because the beam path necessary for the high beam function is a least partially blocked by the additional aperture shutter plate.
A solution is described in US 2009/0303741, in which the light is deflected into the overhead region with an optical fiber disposed between the aperture shutter and the secondary lens. The disadvantage with this solution is that with the optical fiber, at least one additional lens component is needed, which leads to higher costs.